JPH07232935A - Chemical-reinforcing method of glass article - Google Patents

Abstract

PURPOSE:To prevent the generation of a deposited material on a glass article by using a specific metal as a material of a tool for holding the glass article at the time of chemical reinforcing the glass article. CONSTITUTION:Ni or Ti is used as the material of the tool for holding the glass article at the time of chemically reinforcing (e.g. dipping in molten potassium nitrate) the glass article. The inside wall of a chemical reinforcing tank of a vessel for the molten alkali salt at the time of chemically reinforcing the glass article is constituted of Ni. Then, the occurrence of fine particles due to corrosion in the conventional stainless steel is eliminated and the deposition on the glass article is prevented.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for chemically strengthening glass articles.

[0002]

2. Description of the Related Art Conventionally, when chemically strengthening glass articles,
Stainless steel has been used as a material for a jig for holding a glass article and a material for an inner wall of a chemical strengthening tank (hereinafter referred to as a chemical strengthening tank) which is a container for molten alkali salt for ion exchange. The reason for this is that stainless steel is widely used as a metal having high corrosion resistance, and its resistance to rust is overwhelmingly stronger than, for example, iron, and is relatively inexpensive. Further, the conventional glass article to be chemically strengthened was not subjected to particularly strict visual inspection, and the generation of fine deposits did not pose a problem, so this method was sufficient. However, in recent years, substances such as glass substrates for magnetic disks, which have a problem of deposits of several hundred liters, have appeared. That is, on a magnetic disk,
The head for writing and reading magnetic signals flies at high altitude of 100Å.

When chemical strengthening is repeated using a jig made of stainless steel, many particles having a size of about 1 μm adhere to the surface of the glass substrate. Such fine particles are suspended in molten potassium nitrate at 400 to 500 ° C., and once attached to the surface of an extremely smooth glass substrate, it is very difficult to remove them in the subsequent washing step. As a result, a magnetic disk made of such a glass substrate easily causes a head crash, resulting in the worst situation in which the information recorded on the disk is destroyed. ED of such small deposits
When S analysis was performed, Fe and Cr were detected.
That is, it is considered that the jig used as the source of iron-chromium and the stainless steel used for the inner wall of the chemical strengthening tank were corroded due to long-time contact with the hot molten potassium nitrate. The occurrence of rust due to corrosion is easily confirmed visually.

Further, in the stainless jig, as it is repeatedly used, it comes into contact with molten potassium nitrate having strong oxidizing power,
Since the cleaning with water is repeated, the corrosion is more likely to proceed.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to solve the drawback of conventional stainless steel jigs, that is, the adhesion of fine particles of iron-chromium to glass articles in the chemical strengthening step.

[0006]

The present invention has been made to solve the above-mentioned problems, and is characterized in that nickel or titanium is used as the material of the jig for chemical strengthening, and more preferably chemical. The inner wall of the strengthening tank is made of nickel.

[0007]

In the present invention, molten potassium nitrate (melting point of about 320
This is due to the fact that nickel or titanium is suitable as a material that does not generate fine particles due to corrosion due to repeated contact with water). All of these metals prevent the progress of corrosion by forming a dense immobile body layer on the surface. Therefore, unlike stainless steel, for example, iron and chromium in the components are selectively corroded, and fine particles are not generated. Furthermore, in the case of titanium, the coefficient of thermal expansion is smaller than that of stainless steel, and since it is a value closer to that of glass, the occurrence of cracking or chipping of the glass article during the cooling process after pulling from molten potassium nitrate occurs in chemical strengthening. It also has the advantage of being difficult.

[0008]

【Example】

[Examples 1 and 2] 1,000 jigs of magnetic disk glass substrates having a diameter of 95 mm were held in a jig, and the inner dimensions were 90 cm × 80 c.
Chemical strengthening was carried out by immersing in a molten potassium nitrate bath at a temperature of 500 ° C. for 8 hours. After pulling up the glass substrate from the molten potassium nitrate bath and cooling it, potassium nitrate adhering in water was washed. The number of deposits was checked when the jig and the chemical strengthening tank were new and after 100, 200 and 500 times of use. The deposits were counted in the usual process, that is, only after rinsing, that is, washing with running water and ultrasonic waves, and after performing precision washing, that is, washing with detergent and scrub.

Comparative Example 1 is a jig made of stainless steel and the inner wall of the chemical strengthening tank is stainless, Example 1 is a jig made of nickel and the inner wall of the chemical strengthening tank is stainless, and Example 2 is a jig made of titanium and chemically strengthened. This is the case when the inner wall of the tank is stainless steel. As for the deposit, 10 discs from each strengthening lot can be arbitrarily selected.
After the sheets were taken out and visually inspected under halogen light, the average number per surface was shown. The results are shown in Table 1.

[0010]

[Table 1]

As can be seen from Table 1, since rust does not occur in the jigs made of nickel and titanium, the adhesion of fine particles is only due to the rust on the wall surface of the chemical strengthening tank. As a result, even if the chemical strengthening is repeated, the amount of deposits is small, and the deposits can be removed by performing precision cleaning after rinsing. On the other hand, in the case of a jig made of stainless steel, the number of deposits rapidly increases as the chemical strengthening is repeated.

It is considered that this is because iron-chromium fine particles are generated and adhere to the surface of the glass substrate due to the progress of corrosion of the jig.

[Examples 3 and 4] In Comparative Example 2, a jig made of stainless steel and the inner wall of the tank is nickel, Example 3 is a jig made of nickel and the inner wall of the tank is nickel, and Example 4 is a jig made of titanium. In addition, the inner wall of the tank is nickel, and the other points are the same as in the first and second embodiments. The results are shown in Table 2.

[0014]

[Table 2]

As can be seen from Table 2, in the combination of the inner wall of the tank made of nickel and the jig made of nickel or titanium,
Even if the chemical strengthening is repeated, no deposit is generated.

On the other hand, even if the inner wall of the tank is made of nickel, when a stainless jig is used, deposits are generated.

[0017]

【The invention's effect】

(1) In the chemical strengthening step, no adhered matter is generated on the glass article. (2) In the case of a jig made of titanium, since the coefficient of thermal expansion is closer to that of glass, cracking and chipping of the glass article are less likely to occur during the cooling process. It is also lighter than stainless steel and the like.

Claims (2)

[Claims] 1. A method for chemically strengthening a glass article, wherein nickel or titanium is used as a material of a jig for holding the glass article when chemically strengthening the glass article. 2. A method of chemically strengthening a glass article, wherein an inner wall of a chemical strengthening tank, which is a container for molten alkali salt when chemically strengthening the glass article, is made of nickel.